Summer is the season of long, hot days spent lounging on a beach or splashing in the waves. It's associated with relaxation and fun, but, in fact, there's a lot of science behind the icons of summertime. National Geographic's "The Science of Summer" explores the mysteries behind the planet's most sweltering season and reveals the fascinating facts that make summer unique. School may be out but that doesn't mean the learning is over; National Geographic's "Science of Summer" explains why millions of people call summer their favorite time of the year.